Presently known composite impact beams comprise a polymer matrix, reinforced with glass fibres or other polymer fibres.
An impact beam may also comprise metal parts, usually on the places where the impact beam receives compression load during impact.
For instance, EP-B1-1 483 137 discloses an impact beam with a polymer matrix and a metal reinforcing structure comprising metal cords which are preferably embedded in a strip. The metal cords are of a type which can absorb relatively high amounts of impact energy. Such an impact beam has an improved resistance to impact resulting from a collision and has an improved integrity during and after the impact. However, when the impact beam is manufactured by means of an injection moulding process, problems of a different nature can occur. It has for instance been found that it is difficult to obtain by injection moulding a reinforcing structure that avoids brittle behaviour of the impact beam during impact. Either a stiff material is obtained with good quasistatic properties and these materials show a brittle failure at impact. When using for instance a PP (Polypropylene) material, these static properties are not sufficient.
Also known are impact beams which are constructed from a semifinished sheet comprising a textile product. The textile product comprises a separate textile layer of non-metallic fibres and a number of metal cords. For instance, US 2006/013990 discloses an impact beam with a semifinished sheet comprising a polymer matrix and a textile product comprising metal cords which are preferably stitched to the separate textile layer. The metal cords are of a type which can absorb relatively high amounts of impact energy. Such an impact beam reduces or solves the problem of migration of the cords during pressing. The known impact beam does however have a few drawbacks. As the metal cords are bond to the layer of non-metallic fibres by means of stitches, it would involve one or more steps in the production process as compared to the only one manufacture step of a common textile product. Besides, as the separated textile layer as well as the stitched steel cords has a good mechanical and chemical anchoring of the polymer matrix, it would be impossible to allow some movements of the steel cords within the matrix. Therefore, much possibility that the metal cords would locally break due to the very high impact forces while impact happens. It has turned out, however, that the fracture resistance to impact resulting from a collision is at a high risk and that structural integrity during and after the impact has dramatically decreased.